1. Field of the Invention
The present invention relates to storage devices, and more particularly, to a method and apparatus for performing read phase auto-calibration of a storage device.
2. Description of the Prior Art
Regarding the reading process of a storage device (DRAM, for example), a reference signal (DQS signal, for example) is generally used to latch the data stream of a data signal. The reference signal passes a comparator and a delay chain to generate a trigger signal for triggering the above-mentioned data stream latch procedure. The trigger signal is generally an output signal of a standard delay cell among the standard delay cells of the delay chain. The output signal of each standard delay cell corresponds to a read phase. For instance, in a delay chain with four standard delay cells, the output ports of the standard delay cells can respectively output trigger signals corresponding to read phases of 90 degrees, 180 degrees, 270 degrees, 360 degrees.
However, in accordance with the reference signal, the read phase of reading the data stored in the storage device is fixed; that is, a designer who utilizes the storage device has to select an output port for outputting the trigger signal from the output ports of the standard delay cells in the first place, wherein the output port is selected according to the related measurement and trial-and-error experiments, and the appropriate read phase for reading the storage device is determined accordingly. The above-mentioned experimenting/designing procedure consumes too much effort, time, and costs. If the related problem occurs in the manufacturing procedure, much more efforts are needed to optimize the printed circuit board of each product, so as to modify the read phase of reading the storage device.